Eilmeldung: Wolfram spaltet aromatische C‐C‐Bindungen

Walter, Marc D.; Tamm, Matthias

doi:10.1002/ange.201001197

Cited by 6 publications

(2 citation statements)

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“…However, as was pointed out by Sattler and Parkin, [14] Goldman, [15] and Walter and Tamm, [16] the validity of the proposed mechanisms needs to be confirmed by means of a computational analysis. Recently, Miscione et al [17] reported an initial theoretical work on this subject.…”

Section: Introductionmentioning

confidence: 88%

“…The mechanism of such a process has not yet been determined, which appeals to computational assistance to understand how the unstrained C À C bond is activated at the molecular level. [16,17] In this work, by performing density functional theory calculations, we studied various possible mechanisms of cleavage of the aromatic C À C bond in quinoxaline (QoxH) by the W-based com-…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]

Liu

Zhang

Gao

2012

Chemistry A European J

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The aromatic C-C bond cleavage by a tungsten complex reported recently by Sattler and Parkin offers fresh opportunities for the functionalization of organic molecules. The mechanism of such a process has not yet been determined, which appeals to computational assistance to understand how the unstrained C-C bond is activated at the molecular level. In this work, by performing density functional theory calculations, we studied various possible mechanisms of cleavage of the aromatic C-C bond in quinoxaline (QoxH) by the W-based complex [W(PMe(3))(4)(η(2)-CH(2)PMe(2))H]. The calculated results show that the mechanism proposed by Sattler and Parkin involves an overall barrier of as high as 42.0 kcal mol(-1) and thus does not seem to be consistent with the experimental observation. Alternatively, an improved mechanism has been presented in detail, which involves the removal and recoordination of a second PMe(3) ligand on the tungsten center. In our new mechanism, it is proposed that the C-C cleavage occurs prior to the second C-H bond addition, in contrast to Sattler and Parkin's mechanism in which the C-C bond is broken after the second C-H bond addition. We find that the rate-determining step of the reaction is the ring-opening process of the tungsten complex with an activation barrier of 28.5 kcal mol(-1) after the first PMe(3) ligand dissociation from the metal center. The mono-hydrido species is located as the global minimum on the potential-energy surface, which is in agreement with the experimental observation for this species. The present theoretical results provide new insight into the mechanism of the remarkable C-C bond cleavage.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]

Liu

Zhang

Gao

2012

Chemistry A European J

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Catalytic Metathesis of Conjugated Diynes

et al. 2012

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Alkyne metathesis has recently witnessed a significant growth in the number of homogeneous catalysts that are able to efficiently promote the formation and cleavage of carboncarbon triple bonds. [1, 2] All well-defined catalyst systems reported to date can be regarded as variants of Schrock-type molybdenum(VI) or tungsten(VI) alkylidyne complexes [3] in which the metal-alkylidyne moiety, MCÀR, is supported by alkoxide, [4] arlyoxide, [5] amido, [6] imidazolin-2-iminato, [7] phosphoraneiminato, [8] or silanolate ligands. [9,10] With a few exceptions, [11] alkyne metathesis usually requires the presence of internal alkynes, such as RCCMe (R = alkyl or aryl), affording the symmetric alkynes RCCR and MeCCMe. To drive these equilibrium reactions to completion, the latter, 2butyne (b.p. = 27 8C), can be continuously removed from the reaction mixtures under vacuum-driven conditions or, as recently shown by Fürstner and co-workers, advantageously by addition of molecular sieves (5 M.S.) to adsorb 2butyne. [9,12] For our part, the molecular-sieve-promoted method was also clearly superior when alkyne homocoupling and ring-closing alkyne metathesis (RCAM) reactions were studied in the presence of catalytic amounts of the tri(tertbutoxy)silanolate-supported tungsten benzylidyne complex 1 (Scheme 1). [10]

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Selective Arene Cleavage by Direct Insertion of Iridium into the Aromatic Ring

et al. 2017

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We report an unprecedented selective cleavage of aromatic C À Cb onds through the insertion of well-defined iridium complexes into the aromatic ring of simple alkylarenes. The insertion occurs at 50-100 8 8Cw ithout the activation of weaker CÀHand CÀCbonds and gives unique metallacycles in high yields.K ey to the success of this approach is metalinduced deformation of the arene ring, whichc reates temporary ring strain and promotes direct and selective insertion of the metal into the otherwise inert arene ring CÀCbonds.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.

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Eilmeldung: Wolfram spaltet aromatische C‐C‐Bindungen

Cited by 6 publications

References 38 publications

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]

Catalytic Metathesis of Conjugated Diynes

Selective Arene Cleavage by Direct Insertion of Iridium into the Aromatic Ring

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Eilmeldung: Wolfram spaltet aromatische C‐C‐Bindungen

Cited by 6 publications

References 38 publications

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe3)4(η2‐CH2PMe2)H]

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe3)4(η2‐CH2PMe2)H]

Catalytic Metathesis of Conjugated Diynes

Selective Arene Cleavage by Direct Insertion of Iridium into the Aromatic Ring

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Product

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Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]

Theoretical Elucidation of the Mechanism of Cleavage of the Aromatic CC Bond in Quinoxaline by a Tungsten‐Based Complex [W(PMe₃)₄(η²‐CH₂PMe₂)H]